Through the use of a series of well-characterized lysozymes, their derivatives and derived peptide fragments, we shall attempt to fully delineate the basis of immune recognition of this prototype protein. For B cells and antibody we shall employ fine specificity analysis, idiotypy and behavior upon isoelectric focussing to delineate the specificity and basis of heterogeneity of antibody populations. For T cells, limiting dilution proliferation assays and T-rosetting will be employed to determine the size and specificity of binding sites. Through the use of lysozyme labelled with high specific activity of radioisotope, processing at the macrophage level will be analyzed.